In the conventional UTRAN/GERAN system implementations the concept of a radio bearer is needed to setup a connection between the radio network controller RNC and the user equipment UE. However, the radio bearer configuration process requires considerable signaling to negotiate the transport quality and bearer parameters. In practice, the bearer structure is hierarchical between several network entities since the UMTS bearer, radio access bearer and transport bearers (i.e. Iu bearer) are needed, in addition to the radio bearers to carry a flow over the radio access network RAN.
This type of a bearer structure adds delay in the flow set-up, and is difficult to update or reconfigure dynamically.
As it is expected that wireless IP traffic will become even more dominant in the future, new requirements for set-up delay, bit rates and dynamic adjustability will be needed for the radio access technologies. However, the current radio bearer concept will not meet these requirements the most efficiently.
It can be noted that an attempt has been made to enhance the bearer concept to become more packet oriented and flexible, as described in 3GPP 25.331, version 6.x. Further, some newer radio systems, other than 3G UTRAN/GERAN, have means to operate without bearers, because of their ad hoc networking nature and the use of random access channel reservations. However, their quality of service mechanisms typically are not as sophisticated as those of 3G UTRAN/GERAN.